The utility model pertains to heat and power engineering and can be used in refrigeration technology.
There is a known refrigerating system comprising a condenser, an evaporator, and a two-stage centrifugal compressor assembly with a built-in electrical motor between the stages. The motor is provided with a cooling system that has coolant feed and discharge ducts connected to the internal cavity of its housing. Further, the condenser inlet is connected to the compressor assembly outlet, and the condenser outlet is connected by one line to the evaporator inlet via the first choke element, and by a second line to the electrical motor cooling system via the second choke element. The evaporator outlet communicates with the compressor assembly inlet, and the gas coolant discharge duct is connected to the outlet of the compressor assembly""s second stage (1).
The drawbacks of this known cooling system are low efficiency and reliability due to the fact that wet vapor can enter the exhaust of the compressor""s first stage; the presence of oil in the system; the narrow range of controllability; and the fact that ecologically safe coolants cannot be used.
There is a known centrifugal compressor assembly for a refrigerating system comprising two centrifugal compressor stages with rotors, diffuser ducts, collection chambers, inlet and outlet tubing for the second stage, and a built-in electrical motor between the compressor assembly""s first and second stages. The rotor of the electrical motor is positioned with the centrifugal stage rotors on one shaft, which is mounted on bearings, and the stator is fixed inside its housing, forming a cooling skirt between them. Further, the motor housing is provided with gas coolant feed and discharge ducts which are connected to the outlet tubing of the compressor assembly""s second stage (1).
The drawbacks of this known centrifugal compressor assembly for a cooling system are low reliability due to the unsatisfactory design of the electrical motor""s cooling system; the lack of total compensation for axial forces on the assembly""s shaft; the large size of the electrical motor; and the fact that basic design solutions cannot be used for small assemblies, such as those with 5 and 8 kW cooling capacities.
For the refrigerating system, this utility model is intended to increase efficiency and reliability while ensuring ecological safety by allowing the use of ecologically safe coolants; it also broadens the range of cooling capacities and control.
For the centrifugal compressor assembly of said system, this utility model is intended to increase reliability, reduce dimensions and broaden the range of use. =p The 5 or 8 kW refrigerating system in this claim comprises a condenser, an evaporator, and a two-stage centrifugal compressor assembly provided with a built-in electrical motor between the compressor stages. The motor has a cooling system with gas coolant feed and discharge ducts which are connected to the motor""s internal cavity. Further, the condenser inlet is connected to the compressor assembly""s outlet, and the condenser outlet is connected by one line to the evaporator inlet via the first choke element, and by a second line to the motor""s cooling system via the second choke element. The evaporator outlet communicates with the compressor assembly""s inlet, and the coolant discharge duct is connected to the outlet of the compressor""s second stage. We propose fitting the system with an additional choke element, a separator vessel, and a recuperative heat exchanger, and providing the electrical motor""s cooling system with a cooling skirt which is insulated from the internal cavity of the motor housing. The cavity of the cooling skirt is located between the stator and the motor housing and is connected to the second coolant feed and discharge ducts. Further, the additional choke element is a heat regulating valve controlled by the coolant pressure and temperature at its inlet, and the separator vessel is mounted in series in the line connecting the condenser outlet to the evaporator, before the first choke element. The separator vessel is connected by the gas phase to the coolant feed duct, and the recuperative heat exchanger is connected by the coolant to the line connecting the evaporator outlet to the condenser inlet, and to the line connecting the condenser outlet to the evaporator inlet, after the separator vessel. Further, the second line from the condenser is connected to the second coolant feed duct, the second coolant discharge duct is connected to the separator vessel, and the additional choke element, located in the second line, is a heat-regulating valve controlled by the temperature and pressure of the coolant in the second coolant discharge duct.
In addition, the first choke element, mounted in the line from the condenser to the evaporator, is a heat-regulating valve controlled by the coolant pressure and temperature at the evaporator outlet.
The refrigerating system is equipped with a device for controlling motor speed according to the temperature of the air leaving the evaporator.
The 5 or 8 kW centrifugal compressor assembly for said refrigerating system in this claim comprises two centrifugal stages with rotors, diffuser valves, collection chambers and inlet and outlet tubing, Further, the first stage outlet tubing is connected to the second stage inlet tubing by a delivery duct. There is a built-in electrical motor between the stages; its rotor is positioned with the compressor stage rotors on one shaft, which is mounted on gasodynamic bearings, and the stator is fixed inside the motor housing, forming a cooling skirt between them. Further, the motor housing is provided with coolant feed and discharge ducts which are connected to the outlet tubing for the compressor assembly""s second stage. For this assembly, we propose forming the stator cooling skirt with lengthwise slots on the surface of the stator in contact with the housing, the ends of which are connected to annular grooves on the on the internal surface of the motor housing. Further, each of the annular grooves is connected to the second coolant feed or discharge ducts, and the feed and discharge ducts are connected to the internal cavity of the motor housing from different sides of the stator.
In addition, there are lengthwise slots on the surface of the stator in contact with the rotor.
The shaft of the centrifugal compressor assembly is mounted on radial, gasodynamic bearings.
The centrifugal compressor assembly is equipped with bilateral, gasodynamic axial bearings mounted on a gimbal suspension on the shaft in the internal cavity of the motor housing, between the stator and one of the coolant feed or discharge ducts.